Japanese Unexamined Patent Publication No. 2013-39895 discloses an example of work machines which includes a duct structure used for guiding an air flow flowing in an engine room to an outlet that is open in a bottom plate forming a bottom surface of the engine room.
In the engine room of the work machine disclosed in Japanese Unexamined Patent Publication No. 2013-39895, an engine is laterally disposed in the left and right direction. An inlet, a heat exchanger, and an axial fan are disposed on the right side of the engine. The heat exchanger is cooled down by outer air taken in from the inlet due to the rotation of the axial fan.
An exhaust air duct having a laterally long box shape is provided so as to extend along a bottom portion of a front section of the engine. The exhaust air duct includes a plurality of board walls each forming a corresponding one of front, rear, left, and right end portions. A ventilation flue that is surrounded by the plurality of board walls and has a rectangular cross section is formed inside the exhaust air duct. Upper and lower ends of the exhaust air duct are open. An upper end opening of the exhaust air duct serves as an air introducing port. A lower end opening of the exhaust air duct serves as an air outlet. The air outlet is connected to the rectangular outlet that is open in the bottom plate forming the bottom surface of the engine room.
The axial fan rotates clockwise when viewed from the right side thereof. Accordingly, the axial fan generates an air flow that swirls around the engine, introduces the generated air flow into the exhaust air duct from the air introducing port, and discharges the air from the outlet. Thus, the exhaust efficiency of the engine room is increased.
Due to integration of devices, and the like, in associations with the reduction in size of work machines, it is difficult to ensure a large space in an engine room. Under the circumstances, the exhaust efficiency directly influences heat exchange, and therefore, it is an important object to achieve in increasing the cooling performance of an engine, or the like, to increase the exhaust efficiency of the engine room.
In this point, in the above-described exhaust air duct, the air introducing port is formed open upward so as to be opposed to a flow of air and has a large size such that the length of the air introducing port corresponds to approximately the entire length of the engine. Moreover, the cross-sectional area of the ventilation flue including the air outlet and the outlet is equal to or larger than the area of the air introducing port. Thus, air can be efficiently introduced into the exhaust air duct with low ventilation resistance.
However, if there is not enough space in front of the engine, the exhaust air duct of Japanese Unexamined Patent Publication No. 2013-39895 cannot be disposed. Specifically, because the engine has a complex shape in which a plurality of parts are combined, the exhaust air duct has to be disposed so as to be separate from a most protruding part of the engine. Therefore, a dead space is disadvantageously generated around the engine.